Operating circuit for electric discharge devices



April 1952 A. H. WILLOUGHBY 2,593,952

OPERATING CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed April 29, 1949 lrwvem t'ov: Ami hows; H. \A/iLLoughb b ad 0 His A k irorne Patented Apr. 22, 1952 'QPEBATING CIRCUIT FOR ELECTRIG DISCHARGE DEVICES.

Anthony H. Willoughby, Rickmansworth, England, assignor to General Electric Company. a

corporation of New York Application April 29, 1949, Serial No. 90,524

In Great Britain November 26,1947

(ill. 315-86) 3 Claims. 1

This invention relates to circuitarrangements for operating gasor vapor-filled electric dischargedevices from a supply whose voltage is sufliciently high to start the discharge when the filling of the device is deionized at or near room temperature; the devices with which the invention is especially, but not exclusively, concerned are high pressure metal vapor discharge lamps. With such devices the pressure of the gas or vapor filling increases as the device assumes its normal operating temperature and it is often the case that a supply voltage capable of starting the discharge when the filling of the device is deionized at or near room temperature is not sufflciently high to start the discharge if the filling Should become deionized at or near the normal operating temperature of the device, when the vapor pressure is very much higher. If, then, the supply should fail temporarily While the device is in operation, for example, owing to accidental tripping of a circuit breaker, the discharge will be extinguished and the device deionized before the supply can be restored, which case the discharge cannot be restarted until the device has cooled down to a sufliciently low temperature. This cooling may take an inconveniently long time, especially if the device is a high pressure metal vapor discharge lamp, and the object of this invention is to provide means for avoiding or reducing this difficulty.

According to the invention an electric circuit arrangement for operating a gasor vapor filled electric discharge device from a main supply whose voltage is sufficiently high to start discharge when the filling of the device is deionized at or near room temperature but not sufiiciently high to start the discharge when the said filling is deionized at or near the normal op erating temperature of the device, comprises a subsidiary supply circuit arranged to be automatically connected immediately to supply the device in response to a failure of the main supply and to maintain a small current through the device, which current is considerably less than the normal operating current of the device but is sufficient to maintain appreciable ionization within the device.

By immediately in the foregoing statement is meant within such a short time after the failure of the main supply that the ionization within the device has not decayed beyond a point at which the subsidiary supply is capable of maintaining a current through the device.

The current maintained through the discharge device by the subsidiary supply circuit in ac- 1 cordance with the invention should preferably be so small as not to prevent the device from cooling down to a temperature at which. the discharge will restart, even in the absence of ionization, when the main supply is restored.

If the main supply is quickly restored before the device has had time to cool down appreciably, the ionization maintained within the device by the subsidiary supply circuit will enable the discharge to restart immediately. The subsidiary supply circuit may be arranged to be automatically disconnected when the main supply is restored, but if the main supply is not restored for a considerable time, the device may have cooled down to a temperature at which the supply voltage is sufficient to restart the discharge whether ionization is or is not present within the device. Accordingly, it is not necessary for the subsidiary supply circuit to remain operative beyond this point and it may be arranged, for the sake of economy, that the subsidiary supply circuit automatically becomes inoperative after a suitable interval of time from the failure of the supply.

Thus, the subsidiary supply circuit may be ar ranged to be automatically disconnected at the end of the said interval by means of a time-regulated switch. But if the subsidiary supply circuit is energized by an electric battery, which will often be convenient since it is required to supply only a relatively small current intermittently, simplicity may be achieved by using a battery which exhausts itself in approximately the said interval of time, so that the subsidiary supply circuit becomes inoperative merely by the exhaustion of the battery. The subsidiary supply circuit may then be arranged to be automatically disconnected, and the battery quickly recharged, if of a rechargeable type, when the main supply is restored.

The switching actions required for the automatic connection and disconnection of the subsidiary supply circuit on failure and restoration of the main supply may readily be effected by means of one or more voltage or current relays whose operation is controlled by the main supply voltage or the operating current of the device, and the same or different relays may be arranged to effect the automatic recharging of a battery as aforesaid, if such a battery is used.

In order to be able to prevent the subsidiary supply circuit from becoming operative when it is required to put the device out of action deliberately, a special manually operated switch may be provided in the subsidiary supply circuit,

and this switch may, if desired. be ganged with the switch normally used for putting the device out of action.

One circuit arrangement in accordance with the invention is illustrated diagrammatically in the accompanying drawing, and will now be described by way of example.

The drawing shows a circuit for operating a high pressure metal (mercury) vapor electric discharge lamp D from a direct current main supply. The lamp terminals T1 and T2, to which the lamp is shown connected, are connected to the supply terminals T3 and T4, which are adapted to be connected to the main supply, the lamp terminal T1 being connected to the positive supply terminal T3 through the contacts 2 associated with a first relay coil C1 and the contacts S1 of the main switch, and the lamp terminal T2 being connected to the negative supply terminal T4 through a ballast resistance R1 and contacts S2 of the main switch. The relay coil C1,"which is arranged to control the operation of contacts i and 2, is connected to the supply leads on one side between the contacts 2 and the main switch contacts S1, and on the other side between the resistance R1 and the main switch contacts S2.

The manually operated main switch S1, S2 is ganged with an auxiliary switch S2. which controls a subsidiary circuit for supplying the lamp D with an ionizing current independently of the main supply, in accordance with the invention. In this subsidiary circuit one contact of the switch S3 is connected to the negative pole of a battery B through the contact l associated with the relay coil C1, and a second relay coil 02 which has a high resistance and which controls contacts 3 and i, and the other contact of the switch S3 is connected directly to the positive pole of the battery 13. The remainder of the subsidiary supply circuit comprises a choke L, a. resistance R3 and contacts 4, which are connected in series between the positive pole of the battery B and lamp terminal T1, and a resistance R2 and contacts 3, connected in series between lamp terminal T2 and the negative pole of the battery. The negative pole of the battery is connected also to the supply lead between the relay contacts 2 and main switch contacts S1.

In operation, when the main switch S1, S2 is closed and the lamp D is running normally on the main supply, the relay coil C1 is operated by the main voltage so as to hold contacts 1 Open and contacts 2 closed. Hence, although the switch S3, since it is ganged with the main switch S1, S2, is also closed, the flow of current in the subsidiary circuit is prevented by the contacts i being kept open, the contacts 3 and 4 also being open, and the main supply current flows through the closed contacts 2, the lamp D and the resistance B1.

In the event of a failure of the main supply, the voltage applied across the coil C1 disappears, with the result that the contacts I close and the contacts 2 open. The switch S3 remains closed, so that a small current generated by the battery B now flows in that part of the subsidiary supply circuit which comprises the relay coil C2, the contacts I and the switch S3, the magnitude of this current being limited by the resistance of the coil 02. Hence the coil C2 is energized and the contacts 3 and 4 associated with the coil C2 therefore close, so that current generated by the battery now flows through the choke L, resistance R3. contacts 4, the lamp D, resistance R2, contacts 3, and back to the battery B. Thus a steady current, of suflicient magnitude to maintain appreciable ionization of the lamp filling, flows through the lamp until the main supply is restored, or until the battery is exhausted, by which time the lamp will have cooled down sufficiently to be capable of restarting on the main supply voltage even if it is in a deionized condition.

On restoration of the main supply, the coil C1 is again energized, so that the contacts 2 close, thus enabling the supply voltage to reach the lamp terminal T1, and the contacts I open, thus disconnecting the coil C2 from the battery .8 and hence causing the contacts 3 and 4 to open and disconnect the battery iromthe lamp. The contacts! and 2 must be so constructed and arranged that contacts 2 close before contacts I open, in order to insure that the supply of the battery current to the lamp cannot cease before the lamp is reconnected to the main supply. During the short interval of time elapsing between the closing of contacts 2 and opening of contacts I, the main supply, in addition to supplying current to the lamp, will produce a circulating current in that part of the circuit comprising contacts 3, resistance R2, and resistance R1, while the battery B will produce a circulating current in that part of the circuit comprising the choke L, resistance Re, contacts 4 and contacts 2. However, these circulating currents are limited by resistances R2 and Rs, respectively, the-resistance R2 being great enough to insure that the greater part or" the main supply current flows through the lamp.

The function of the choke L, in the subsidiary supply circuit,,is to produce an inductive pulse at each of the switching operations resulting from a main failure or restoration, which pulse will insure that ionization is maintained in the lamp during and immediately after each switching operation.

When the main supply is switched off, by operation of the switch S1, S2, the switch S3 is also opened; hence the coil C2 cannot be ener-v gized by the battery B, so that the subsidiary supply circuit does not then operate.

For a lamp adapted to be operated from a direct current main supply of or 220 volts, and whose normal operating current is from 50 to 100 amperes, the voltage across the lamp during normal operation being from 60 to 70 Volts, a battery of volts may be employed to provide the subsidiary supply and to produce an ionizing current of approximately 5 amperes.

The appended claims are intended to cover any modifications coming within the true spirit and scope of the invention, which scope obviously includes variations in the specific lamp employed, in the supply and subsidiary voltages, in the relays and switches, and in the ballasting and current limiting resistances and inductances utilized in connection therewith.

What I claim as new and desire to secure by Letters Patent of the Unitedv States is:

1. An electric circuit arrangement for assuring immediate restarting of an electric discharge lamp upon restoration of a supply voltage after an interruption thereof, comprising a discharge lamp containing an ionizable medium exhibiting a comparatively low starting voltage characteristic when deionized at ambient temperature and also when ionized near normal operatingtemperature, but exhibiting a high starting voltage characteristic when deionized above ambient temperature, a voltage supply,. a main switch provided with a plurality of ganged contacts, a ballasting impedance and a first relay having an operating coil a normally open contact and a normally closed contact, a main discharge circuit constituted by connecting one of said main switch contacts, said normally open relay contact, said lamp and said ballasting impedance in series across said supply, a first control circuit for said first relay constituted by connecting the coil thereof, in series with said one switch contact, across said supply, a subsidiary voltage supply, a current limiting impedance and a second relay having an operating coil and a pair of normally open contacts, a subsidiary supply circuit constituted by connecting said subsidiary voltage supply, in series with said current limiting impedance and through respective contacts of said second relay across respective sides of said lamp, and a second control circuit for said second relay constituted by connecting the coil thereof, in series with said other main switch contact and the normally closed contact of said first relay, across said subsidiary supply.

2. An electric circuit arrangement for assuring immediate restarting of an electric discharge lamp upon restoration of a supply voltage after an interruption thereof, comprising a discharge lamp containing an ionizable medium exhibiting a comparatively low starting voltage characteristic when deionized at ambient temperature and also when ionized near normal operating ternperature, but exhibiting a high starting voltage characteristic when deionized above ambient temperature, a voltage supply, a main switch provided with a plurality of ganged contacts, a ballasting impedance and a first relay having an operating coil, a normally open contact and a normally closed contact, a main discharge circuit constituted by connecting one of said main switch contacts, said normally open relay contact, said lamp and said ballasting impedance in series across said supply, a first control circuit for said first relay constituted by connecting the coil thereof, in series with said one switch contact, across said supply, a subsidiary voltage supply, a current-limiting impedance and a second relay haw'ng an operating coil and a pair of normally open contacts, a subsidiary supply circuit constituted by connecting said subsidiary voltage supply, in series with said current-limiting impedance and through respective contacts of said second relay across respective sides of said lamp, and a second control circuit for said second relay constituted by connecting the coil thereof, in series with said other main switch contact and the normally closed contact of said first relay, across said subsidiary supply, said subsidiary voltage supply and said current-limiting impedance having magnitudes so related as to provide a small current through said lamp sufiicient to maintain appreciable ionization therein.

3. An electric circuit arrangement for assuring immediate restarting of an electric discharge lamp upon restoration of a supply voltage after an interruption thereof, comprising a. discharge lamp containing an ionizable medium exhibiting a comparatively low starting voltage characteristic when deionized at ambient temperature and also when ionized near normal operating temperature, but exhibiting a high starting voltage characteristic when deionized above ambient temperature, a voltage supply, a main switch provided with a plurality of ganged contacts, a ballasting impedance and a first relay having an operating coil, a normally open contact and a normally closed contact, a main discharge circuit constituted by connecting one of said main switch contacts, said normally open relay contact, said lamp and said ballasting impedance in series across said supply, a first control circuit for said first relay constituted by connecting the coil thereof, in series with said one switch contact, across said supply, a subsidiary voltage supply, a current-limiting impedance and a second relay having an operating coil and a pair of normally open contacts, a subsidiary supply circuit constituted by connecting said subsidiary voltage supply, in series with said current-limiting impedance and through respective contacts of said second relay across respective sides of said lamp, and a second control circuit for said second relay constituted by connecting the coil thereof, in series with said other main switch contact and the normally closed contact of said first relay, across said subsidiary supply, said subsidiary voltage supply being a battery having a voltage output sufiicient for maintaining appreciable ionization within said lamp and a capacity limited to attain exhaustion by the time said lamp has cooled substantially to ambient temperature.

ANTHONY H. WILLOUGHBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Germany Jan. 10, 1940 

